Microscanner D-Series Portable Infrared Thermometer from Exergen

The D-Series is an entirely different type of instrument than conventional temperature measuring devices. Designed specifically for the highest possible accuracy, it is the only infrared instrument which can be certified as to NIST-tracable accuracy on real surfaces of unknown emissivity, while completely free of contact errors and heat sinking errors of contact devices.

The D-Series is an entirely different type of instrument than conventional temperature measuring devices. Designed specifically for the highest possible accuracy, it is the only infrared instrument which can be certified as to NIST-tracable accuracy on real surfaces of unknown emissivity, while completely free of contact errors and heat sinking errors of contact devices.

1. Pre-set Emissivity errors

The true emissivity of a surface is known only approximately. Conventional IR devices without Exergen's Automatic Emissivity Compensation System can only display an approximate temperature over their entire temperature range. The "accuracy" specifications given by most manufacturers are only for a "black body" calibration and do not hold outside laboratory conditions. Black body calibrations do not include emissivity shifts, ambient change effects on the target, and other phenomena that introduce significant errors.

2. Emissivity shift errors

Even if an IR "gun" is set to the correct emissivity to read a surface accurately at a particular temperature, it does not mean that the IR "gun" will read the same target correctly at other temperatures. Emissivity of virtually all surfaces changes with temperature. A common assumption for conventional IR thermometry is that emissivity is constant with changes in target surface temperature. Real materials do not have this characteristic.

3. User Adjustment Errors

A setting of emissivity = 0.9 on an IR "gun" from one manufacturer will not necessarily match that of another IR "gun" manufacturer. There are no standards set in the industry on the precise measurement and meaning of "emissivity".

Also, Quality Assurance programs should not rely upon any instrument that allows users to alter the instrument settings and to let it display whatever the user wishes.

4. Background Reflection Errors

Even if emissivity is constant (see #2), there are still errors induced by changing ambient temperatures. For example, with emissivity = 0.9, ambient reflections account for 10% of the signal that the IR "gun" will see. If ambient changes, the IR "gun" will display a different target temperature, even if the target remains at the same temperature.

5. Contact Errors

Thermocouples, RTDs. thermistors, and other contact devices only measure their own temperature. They do not measure surface temperature. Published "Accuracy" specifications are for the probes only, not the surfaces they must measure. Users must guarantee that the probes are brought the same temperature as the surface. Can you guarantee that your probes are brought to the same temperature as the targets to be measured?

6. Friction heating errors

For moving surfaces, a contact probe is prone to frictional heating. The size of the error is dependent on the roughness of the surface, the speed, the coating on the probe, and so on. It is impossible to control all the variables.

7. Heat sinking errors

For most non-metals, heat sinking errors can be quite large. The heat transfer rate of the metal leads required on "contact probes" conducts heat faster than the target material can replace, resulting in unknown and fairly large errors. In general, the less dense the target material, the larger the heat sinking error with a contact probe.

8. Time based errors

Contact temperature probes are slow. The temperature of a target can change more quickly than most probes, resulting in errors in real time measurement.